Fibers sized with polyethereketoneketones

ABSTRACT

Fibers sized with a coating of amorphous polyetherketoneketone are useful in the preparation of reinforced polymers having improved properties, wherein the amorphous polyetherketoneketone can improve the compatibility of the fibers with the polymeric matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/148,157, filed Aug. 16, 2011 which is a national stage applicationunder 35 U.S.C. §371 of PCT/US2010/023129, filed Feb. 4, 2010, whichclaims benefit to U.S. Provisional Application No. 61/150,129, filed onFeb. 5, 2009.

FIELD OF THE INVENTION

The invention relates to fibers sized with a coating of amorphouspolyetherketoneketone as well as reinforced polymers that include suchsized fibers.

DISCUSSION OF THE RELATED ART

Various chemical treatments exist for the surfaces of fibers such asglass fibers and carbon fibers to aid in their handling, improveprocessability for compounding and downstream processes such asinjection molding, and improve strength and other properties forspecific end-use applications. Before bundling the filaments togetherafter formation, a coating composition or sizing composition is appliedto at least a portion of the surface of the individual filaments toprotect them from abrasion and to assist in processing. Sizingcompositions may provide protection through subsequent processing steps,such as those where the fibers pass by contact points as in the windingof the fibers and strands onto a forming package, drying theaqueous-based or solvent-based sizing composition to remove the water orsolvent (if the sizing has been applied to the fibers using a solution),twisting from one package to a bobbin, beaming to place the yarn ontovery large packages ordinarily used as the warp in a fabric, chopping ina wet or dry condition, roving into larger bundles or groups of strands,unwinding for use as a reinforcement, and other downstream processes.

In addition, sizing compositions can play a dual role when placed fibersthat reinforce polymeric matrices in the production of fiber-reinforcedplastics. In such applications, the sizing composition providesprotection and also can provide compatibility between the fiber and thematrix polymer or resin. For instance, fibers in the forms of woven andnonwoven fabrics and mats, rovings and chopped strands have been usedwith resins, such as thermosetting and thermoplastic resins, forimpregnation by, encapsulation by, or reinforcement of the resin. Insuch applications, it is desirable to maximize the compatibility betweenthe surface and the polymeric resin while also improving the ease ofprocessability and manufacturability. However, many polymeric resins,especially highly crystalline engineering thermoplastics such ascrystalline polyaryletherketones, do not exhibit good adhesion tovarious fiber surfaces. Poor adhesion at the interface between the fibersurface and the polymeric resin matrix makes it difficult to take fulladvantage of the property improvements potentially realizable throughincorporation of the fibers into such matrices. Additionally, many ofthe sizing compositions that have been developed to date haveunsatisfactory stability at the high processing temperatures typicallyrequired to admix fibers into engineering thermoplastics.

Accordingly, it would be desirable to develop alternative approaches toenhance the compatibility of engineering thermoplastics and the likewith fibers of various types so that composites having improvedproperties can be obtained.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a sized fiber comprising a fiber having acoating of amorphous polyetherketoneketone, as well as a method ofmaking a sized fiber comprising coating a fiber with amorphouspolyetherketoneketone. In another aspect, the invention provides areinforced polymer comprising a polymer matrix and sized fiberscomprising fibers having a coating of amorphous polyetherketoneketone.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE Shows micrographs of fibers sized with PEKK and PEEK, anddemonstrates the failure mode in fibers of each sizing.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

Sized fibers in accordance with the present invention are advantageouslymanufactured by coating fibers with a polymeric composition comprised ofan amorphous (non-crystalline) polyetherketoneketone.

The amorphous polyetherketoneketones suitable for use in the presentinvention comprise (and preferably consist essentially of or consist of)repeating units represented by the following Formulas I and II:-A-C(═O)—B—C(═O)—  I-A-C(═O)-D-C(═O)—  IIwhere A is a p,p′-Ph-O-Ph- group, Ph is a phenylene radical, B isp-phenylene, and D is m-phenylene. The Formula I:Formula II (T:I) isomerratio in the polyetherketoneketone is selected so as to provide anamorphous polymer. An amorphous polymer, for purposes of this invention,means a polymer that does not exhibit a crystalline melting point bydifferential scanning calorimetry (DSC).

Polyetherketoneketones are well-known in the art and can be preparedusing any suitable polymerization technique, including the methodsdescribed in the following patents, each of which is incorporated hereinby reference in its entirety for all purposes: U.S. Pat. Nos. 3,065,205;3,441,538; 3,442,857; 3,516,966; 4,704,448; 4,816,556; and 6,177,518.Mixtures of polyetherketoneketones may be employed.

In particular, the Formula I:Formula II ratio (sometimes referred to inthe art as the T/I ratio) can be adjusted as desired by varying therelative amounts of the different monomers used to prepare thepolyetherketoneketone. For example, a polyetherketoneketone may besynthesizing by reacting a mixture of terephthaloyl chloride andisophthaloyl chloride with diphenyl ether. Increasing the amount ofterephthaloyl chloride relative to the amount of isophthaloyl chloridewill increase the Formula I:Formula II (T/I) ratio. Generally speaking,a polyetherketoneketone having a relatively high Formula I:Formula IIratio will be more crystalline than a polyetherketoneketone having alower Formula I:Formula II ratio. An amorphous polyetherketoneketonehaving a T/I ratio of from about 55:45 to about 65:35 is particularlysuitable for use in the present invention.

Suitable amorphous polyetherketoneketones are available from commercialsources, such as, for example, certain of the polyetherketoneketonessold under the brand name OXPEKK by Oxford Performance Materials,Enfield, Conn., including OXPEKK-SP polyetherketoneketone.

The polymeric composition used as a fiber sizing may additionally becomprised of components other than the amorphous polyetherketoneketone,such as stabilizers, pigments, processing aids, fillers, and the like.If the sizing is to be applied to the fibers in solution form, suchadditional components should preferably be soluble in the solvent ormixture of solvents employed. In certain embodiments of the invention,the polymeric composition consists essentially of or consists ofamorphous polyetherketoneketone. For example, the polymeric compositionmay be free or essentially free of any type of polymer other thanamorphous polyetherketoneketone.

The present invention is useful in connection with any type of fiber,but particularly fibers that are to be used as reinforcements or fillersin polymeric matrices. Suitable fibers include, for example, glassfibers, carbon fibers, polymeric fibers, metallic fibers, mineral(ceramic, inorganic) fibers and the like. Glass fibers (fiberglass) maybe obtained from any type of glass, e.g., A glass, E glass, S glass, orD glass. Carbon fibers (which include graphite fibers) are typicallyprepared by pyrolysis of organic or polymeric fibers (such as PAN).Polymeric fibers include fibers made from any of the known types ofthermoplastic polymers such as polyamides, polyolefins, polyaramids,polyesters, poly(p-phenylene-2,6-benzobisoxazole)(PBO), and the like.Suitable metallic fibers include fibers prepared using any type of metalor metal alloy, such as iron, steel, aluminum, aluminum alloys, copper,titanium, nickel, gold, silver and the like. Mineral fibers that can beused in the present invention are fibers made from natural or syntheticminerals, refractory oxides or metal oxides and include, but are notlimited to, mineral wool, rock wool, stone wool, basalt fibers, aluminafibers, beryllia fibers, magnesia fibers, thoria fibers, zirconiafibers, silicon carbide fibers, quartz fibers, boron fibers, asbestosfibers and high silica fibers and the like.

Fibers of any diameter or length may be sized with a coating ofamorphous polyetherketoneketone in accordance with the presentinvention. For example, the fiber may be from 1 micron to 1 mm indiameter. Typically, the fiber is many times longer than its diameter.For example, the fiber length may be at least 10, 100, 1000 or 10,000times the fiber diameter.

In one embodiment of the invention, the amorphous polyetherketoneketoneis applied to the fiber as a sizing composition comprised of thepolyetherketoneketone and a suitable solvent or mixture of solvents andthe solvent or solvent mixture then removed by drying so as to deposit arelatively thin coating of the polyetherketoneketone on the fibersurface. Any substance capable of dissolving the polyetherketoneketonemay be utilized as the solvent, including, for example, halogenated(preferably, chlorinated) organic compounds such as o-dichlorobenzene,1,2-dichloroethane, dichloromethane (methylene chloride),alpha-chloronaphthalene and tetrachloroethylene. Other suitable solventsmay include benzophenone, diphenylsulfone, 2-phenylphenol,p-methoxyphenol, 2-methoxynaphthalene, ethyl-4-hydroxybenzoate,N-cyclohexyl-2-pyrrolidone, pentafluorophenol, dimethylphthalate,nitrobenzene and phenyl benzoate. Aqueous mineral acids (e.g., sulfuricacid and/or nitric acid) are examples of other solvents that could beused for this purpose. In one embodiment of the invention, the amorphouspolyetherketoneketone is synthesized in a suitable solvent and theresulting polymerization reaction product used as the sizing composition(thereby avoiding the need to isolate the polyetherketoneketone from thepolymerization reaction mixture and then redissolve it). The solventshould be selected based on its compatibility with the fibers that areto be sized in accordance with the present invention. For example, thesolvent should not dissolve or degrade the fibers.

The amorphous polyetherketoneketone preferably forms a relatively thincoating on the fiber surface. For example, the polyetherketoneketonecoating may be from about 1 to about 50 microns thick. In one embodimentof the invention, the fiber surfaces are completely covered by thepolyetherketoneketone coating, although in other embodiments certainportions of the fiber surfaces remain uncoated. Typically, the amorphouspolyetherketoneketone coating may comprise from about 0.01 to about 10%by weight of the sized fibers.

The fiber may be in the form of individual filaments, twisted yarns,threads, strands, rovings, mats, meshes, scrims or a fabric (woven ornon-woven) at the time it is sized with the amorphouspolyetherketoneketone. After sizing, the fibers may be further processed(e.g., individual filaments may be sized and the sized filaments thenconverted into yarns, threads, strands, rovings, mats, meshes, scrims,woven fabric, non-woven fabric and the like). In one embodiment, thefiber is in continuous form (e.g., an unbroken filament, thread, strandor yarn) at the time it is sized, but then converted into discontinuousform by cutting, chopping or other such operation. The discontinuoussized fibers may, for example, be from about 0.5 to about 20 mm inlength. The sized fibers may be used, in continuous or discontinuousform, in the manufacture of fiber reinforced composites.

Means for applying the sizing composition include, but are not limitedto, pads, sprayers, rollers or immersion baths, which allow asubstantial amount of the surfaces of the individual filaments of thefiber to be wetted with the sizing composition. The sizing compositionmay be applied to the fibers by dipping, spraying, roll coating,extruding, pultrusion, or the like. In one embodiment, the sizingcomposition is applied to the fibers continuously.

If solvent is present in the sizing composition, the solvent is removedafter the sizing composition is applied to the fiber. The solvent may beremoved by heating the fiber to evaporate the solvent, by allowing thesolvent to evaporate at ambient temperature and pressure and/or bysubjecting the fiber to vacuum. When the solvent is removed by heating,the temperature will vary depending on the types of solvent and fiberused. The solvent may be removed continuously, for example, by passingthe fiber through a heater, such as a tube furnace. The time required toremove the solvent will vary depending on the temperature and thesolvent, however, the time required is typically several seconds toseveral hours, preferably 10 to 20 seconds. If an acidic solution hasbeen used, the fibers may be passed through water to remove residualacid (extractive dilution) or passed through a basic solution to removeand/or neutralize residual acid.

Although sized fibers accordance with the present invention can becombined with or compounded into any type of polymeric matrix, includingthermoplastic or thermosettable polymeric matrices, they areparticularly useful where it is desired to provide fiber reinforcementto a polymeric-matrix comprised, consisting essentially of, orconsisting of a crystalline and/or high temperature thermoplastic asthese materials often exhibit interfacial adhesion to various types offiber surfaces that is not completely satisfactory. A sizing ofamorphous polyetherketoneketone on the fiber in accordance with thepresent invention helps to improve such adhesion, thereby enhancing themechanical and other properties of the resulting composite. Suitablecrystalline and/or high temperature thermoplastics include, but are notlimited to, polyaryletherketones (such as crystalline polyetherketone(PEK), crystalline polyetheretherketone (PEEK), crystallinepolyetherketoneketone (PEKK), polyetheretheretherketone (PEEEK),polyetheretherketoneketone (PEEKK), polyetherketoneetheretherketone(PEKEKK), and polyetherketoneketoneketone (PEKKK)), polyimides,polyetherimides, polyamideimides, polysulfones, polyethersulfones,polyarylethers, polycarbonates, liquid crystal polymers, polyphenylenesulfides, polyarylenes (polyphenylenes), polyamides, polyphthalamides,polyaromatic esters and the like.

In one embodiment of the invention, chopped fibers sized with amorphouspolyetherketoneketone may be mixed with a polymeric resin and suppliedto a compression- or injection-molding machine to be formed intofiber-reinforced composites. Typically, the chopped fibers are mixedwith pellets of a thermoplastic polymer resin in an extruder. Forexample, polymer pellets can be fed into a first port of a twin screwextruder and the chopped sized fibers then fed into a second port of theextruder with the melted polymer to form a fiber/resin mixture.Alternatively, the polymer pellets and chopped fibers can be dry mixedand fed together into a single screw extruder where the resin is meltedand the fibers are dispersed throughout the molten resin to form afiber/resin mixture. Next, the fiber/resin mixture is degassed andformed into pellets. The fiber/resin pellets can then be fed to amolding machine and formed into molded composite articles that have asubstantially homogeneous dispersion of fibers throughout the compositearticle.

The sized fibers of the present invention may also be used in long-fiberthermoplastic applications. Fiber-reinforced thermoplastic polymerstructural components can be manufactured from long fiber thermoplastic(LFT) granulates (pellets), glass mat thermoplastic (GMT) sheets, orpultruded sections wherein the fibers have been sized with amorphouspolyetherketoneketone. Long fiber-reinforced granulates can comprisesized fiber bundles encapsulated with a thermoplastic through a cablecoating or a pultrusion process. The LFT granulates, which containfibers equal in length to the pellet, e.g., 1 to 25 mm, can be injectionmolded, but can also be extrusion compression molded in order topreserve fiber length in the finished product.

Polymer components reinforced with sized fibers in accordance with thepresent invention may also be manufactured using continuous in-lineextrusion methods known in the art. Such methods involve theplastication of a polymer in a first single screw extruder from whichthe output is fed to a second single screw extruder. Fibers areintroduced in the polymer melt in the second extruder, either inchopped-segmented form or as continuous strands under a predeterminedtension. The fiber-reinforced polymer is fed into an accumulator andthen applied automatically or in a separate step to a compressionmolding tool wherein the fiber-reinforced polymer is shaped as requiredfor a particular application. Alternatively, the fiber-reinforcedpolymer may be continuously extruded onto a conveyor and sectionedthereupon. The conveyor delivers the sectioned fiber-reinforced polymerto a placement assembly which removes the sectioned material from theconveyor and places the material upon the compression molding tool.

The process of compounding and molding the sized reinforcing fiber andthe matrix resin to form a composite may be accomplished by any meansconventionally known in the art. Such compounding and molding meansinclude, but are not limited to, extrusion, wire coating, blow molding,compression molding, injection molding extrusion-compression molding,extrusion-injection-compression molding, long fiber injection, andpushtrusion.

The orientation of the sized fibers within the polymeric matrix of thecomposite produced in accordance with the present invention may bevaried and controlled as desired using the techniques known to thoseskilled in the field. For example, the fibers may be continuous andaligned, or discontinuous and aligned, or discontinuous and randomlyoriented.

The amount of fiber included in the composite is generally about 1% toabout 90% by weight, based on the total weight of the compositeformulation.

The amorphous polyetherketoneketone provides a coating on thereinforcing fibers that improves compatibility and adhesion with theresin matrix, and results in composites with more desirable propertiessuch as higher short-term and long-term mechanical properties.

Reinforced polymers prepared in accordance with the present inventionmay be utilized in any of the end use applications where such materialsconventionally are employed or have been proposed to be employed.Representative applications include composites for aerospace/aircraft,automobiles and other vehicles, boats, machinery, heavy equipment,storage tanks, pipes, sports equipment, tools, biomedical devices(including devices to be implanted into the human body, such asload-bearing orthopedic implants), building components, and the like.Benefits of the invention described herein include higher tensilestrength, higher compressive strength, improved resistance to crackinitiation and propagation, greater creep resistance, and higherresistance to attack by various chemicals and solvents, as compared toreinforced polymers prepared using fibers that are not sized withamorphous polyetherketoneketone.

Fiber-reinforced composites in accordance with the present inventioncan, for example, be used to prepare laminar panels that are stacked andbonded to each other or can be used as face sheets in the production ofsandwich panels having honeycomb or foamed cores.

EXAMPLES Example 1

Sizing a fiber from a solution—A solution of an amorphous grade ofPolyetherketoneketone (A-PEKK) such as OXPEKK SP from Oxford Performancematerials) with a high ratio of isophthalate (T/I=55-45 to 65-35 butmost preferably 60/40) is produced by dissolving XX gm of PEKK in 100 gmof concentrated sulfuric acid. The solution is placed in a bath ofsuitable construction so as not to react with the strong mineral acidand a glass fiber yarn made from a group of fibers is passed through thebath so as to produce a fairly even coating of the solution. The acidicsolution is then neutralized or simply diluted by passage through asecond bath containing a basic solution or just water. The act ofneutralizing or diluting the solution thus renders the polymer insolubleand leaves a coating of the polymer on the fiber.

Example 2

Sizing the fiber by powder coating and heating—A fine powder is producedfrom an amorphous grade of A-PEKK, as described in example 1, and usedto powder coat a metal fiber. Two general methods can be employed forthe powder coating. In the first, an electrostatic spray of the finepowder is applied to the fiber just prior to the fiber entering an ovenheated to a temperature such that the A-PEKK melts (c.a 320° C.) andforms a generally continuous coating on the fiber. Alternatively thefiber can be heated prior to entering a fluidized bath containing thefine A-PEKK powder. More details on specific powder coating methods canbe found in references such as: Powder Coating, The Complete Finisher'sHandbook, 1997, Powder Coating Inst., ISBN: 0964309106 or OrganicCoatings: Science and Technology (Society of Plastics EngineersMonographs) (Vol 2), Z. W. Wicks Jr, Frank N. Jones and S. P. Pappas(Authors). For the application described here there is no need for animpermeable A-PEKK coating but rather only a reasonably complete layerof A-PEKK needs to be applied.

Example 3

Sizing Woven Mats—Complete woven, or otherwise formed mats of metal orglass strands can be sized after production by passing the preformed mator cloth through the solution described in example 1 or by powdercoating as described in example 2.

Example 4

Incorporation of the A-PEKK sized fibers into a matrix—The A-PEKK sizedfibers can be incorporated into an article by any manner of polymerprocessing. Chopped fiber is routinely incorporated by compounding thefiber into a polymer using a twin screw extruder and continuous fiberincorporation can be accomplished by pultrusion etc. As the A-PEKKsizing is compatible with a variety of other high temperature polymermatrices and PEKK has very good adhesion properties the A-PEKK sizingcan diffuse into the matrix promoting incorporation or dispersion of thefibers within the matrix polymer and improve the adhesion of the fibersto the matrix. The pictures of the FIGURE illustrate the adhesiondeveloped by PEKK to a glass fiber vs. that developed by another hightemperature polymer, in this case polyetheretherketone PEEK. As thepicture illustrates the failure in the PEKK composite is cohesive as thefailure is in the PEKK matrix. The fracture surface in this case showssignificant ductility produced as a consequence of the effective loadtransfer between the fiber and the PEKK matrix. In contrast, the failurein the PEEK system is adhesive as the fibers are cleanly pulled from thematrix. The fractured surface shows a clean brittle rupture process,indicating that in this case the interaction of the fiber with thematrix is not as effective. Load transfer is not expected to beefficient in this system. The energy of breaking a piece by cohesivefailure is dependant on the strength of the matrix itself and isgenerally regarded as higher than an adhesive failure.

What is claimed is:
 1. A sized fiber comprising a fiber having a coatingof amorphous polyetherketoneketone, said coating comprising about 0.01to about 10% by weight of the amount of coating in the sized fiber andhaving a thickness of about 1 micron to about 50 microns, wherein saidcoating surrounds said fiber surfaces, and wherein the amorphouspolyetherketoneketone is comprised of repeating units represented byformulas I and II:-A-C(═O)—B—C(═O)—  I-A-C(═O)-D-C(═O)—  II wherein A is a p,p′-Ph-O-Ph- group, Ph is aphenylene radical, B is p-phenylene, and D is m-phenylene and the isomerratio of formula I:formula II (T:I) ranges from about 55:45 to about65:35.
 2. The sized fiber of claim 1, wherein said fiber is amonofilament.
 3. The sized fiber of claim 1, wherein said fiber is amultifilament.
 4. The sized fiber of claim 1, wherein said fiber has adiameter of about 50 microns to about 1 mm.
 5. The sized fiber of claim1, wherein said fiber is selected from the group consisting of glassfibers, carbon fibers, mineral fibers, metal fibers and polymericfibers.
 6. The sized fiber of claim 1, where said fiber is made from oneor more components selected from the group consisting of glass, graphitefibers, polyamides, polyolefins, polyaramids, polyesters,poly(p-phenylene-2,6-benzobisoxazole)(PBO), iron, steel, aluminum,aluminum alloys, copper, titanium, nickel, gold, silver, mineral wool,rock wool, stone wool, basalt fibers, alumina fibers, beryllia fibers,magnesia fibers, thoria fibers, zirconia fibers, silicon carbide fibers,quartz fibers, boron fibers, and asbestos fibers.
 7. A reinforcedpolymer comprising a polymer matrix and sized fibers of claim
 1. 8. Thereinforced polymer of claim 7, wherein said polymer matrix is comprisedof a one or more thermoplastics selected from the group consisting ofpolyaryletherketones (PAEK), polyetheretherketone (PEEK),polyetherketoneketone (PEKK), polyetheretheretherketone (PEEEK),polyetheretherketoneketone (PEEKK), polyetherketoneetheretherketone(PEKEKK), polyetherketoneketoneketone (PEKKK)), polyimides,polyetherimides, polyamideimides, polysulfones, polyethersulfones,polyarylethers, polycarbonates, liquid crystal polymers, polyphenylenesulfides, polyarylenes (polyphenylenes), polyamides, polyphthalamides,and polyaromatic esters.
 9. The reinforced polymer of claim 7, whereinsaid polymer matrix is comprised of a crystalline poly(aryletherketone).10. A pellet comprising sized fibers and one or more thermoplasticsselected from the group consisting of polyaryletherketones (PAEK),polyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetheretheretherketone (PEEEK), polyetheretherketoneketone (PEEKK),polyetherketoneetheretherketone (PEKEKK), polyetherketoneketoneketone(PEKKK)), polyimides, polyetherimides, polyamideimides, polysulfones,polyethersulfones, polyarylethers, polycarbonates, liquid crystalpolymers, polyphenylene sulfides, polyarylenes (polyphenylenes),polyamides, polyphthalamides, and polyaromatic esters; wherein saidsized fibers comprise a fiber having a coating of amorphouspolyetherketoneketone, said coating comprising about 0.01 to about 10%by weight of the amount of coating in the sized fibr and having athickness of about 1 micron to about 50 microns, wherein said coatingsurrounds said fiber surfaces, and wherein the amorphouspolyetherketoneketone is comprised of repeating units represented byformulas I and II:-A-C(═O)—B—C(═O)—  I-A-C(═O)-D-C(═O)—  II wherein A is a p,p′-Ph-O-Ph- group, Ph is aphenylene radical, B is p-phenylene, and D is m-phenylene and the isomerratio of formula I: formula II (T:I) ranges from about 55:45 to about65:35.
 11. A thermoplastic pellet comprising the sized fibers claim 1,said fibers having a length and a diameter such that said fiber lengthis at least 10 times the fiber diameter, and one or more thermoplasticsselected from the group consisting of polyaryletherketones (PAEK),polyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetheretheretherketone (PEEEK), polyetheretherketoneketone (PEEKK),polyetherketoneetheretherketone (PEKEKK), polyetherketoneketoneketone(PEKKK)), polyimides, polyetherimides, polyamideimides, polysulfones,polyethersulfones, polyarylethers, polycarbonates, liquid crystalpolymers, polyphenylene sulfides, polyarylenes (polyphenylenes),polyamides, polyphthalamides, and polyaromatic esters.
 12. A yarn,thread, strand roving, mat, mesh, scrim, woven fabric, or non-wovenfabric comprising sized fibers, said sized fibers comprising a fiberhaving a coating of amorphous polyetherketoneketone, said coatingcomprising about 0.01 to about 10% by weight of the amount of coating inthe sized fiber and having a thickness of about 1 micron to about 50microns, wherein said coating surrounds said fiber surfaces, and whereinthe amorphous polyetherketoneketone is comprised of repeating unitsrepresented by formulas I and II:-A-C(═O)—B—C(═O)—  I-A-C(═O)-D-C(═O)—  II wherein A is a p,p′Ph-O-Ph- group, Ph is aphenylene radical, B is p-phenylene, and D is m-phenylene and the isomerratio of formula I; formula II (T:I) ranges from about 55:45 to about65:35.
 13. A method of making a sized fiber, said method comprisingcoating a fiber with a sizing composition comprising amorphouspolyetherketoneketone, said coating comprising about 0.01 to about 10%by weight of the amount of coating in the sized fiber and having athickness of about 1 micron to about 50 microns, wherein said coatingsurrounds said fiber surfaces, and wherein the amorphouspolyetherketoneketone is comprised of repeating units represented byformulas I and II:-A-C(═O)—B—C(═O)—  I-A-C(═O)-D-C(═O)—  II wherein A is a p,p′-Ph-O-Ph- group, Ph is aphenylene radical, B is p-phenylene, and D is m-phenylene and the isomerratio of formula I: formula II (T:I) ranges from about 55:45 to about65:35.
 14. The method of making the sized fiber of claim 13, where thefiber is in the form of twisted yarns, threads, strands, rovings, mats,meshes, scrims, woven fabric, or non-woven fabric and is sized with theamorphous polyetherketoneketone, thereby providing the sized fiber.